The xanthophyll cycle of Mantoniella squamata converts violaxanthin into antheraxanthin but not to zeaxanthin: consequences for the mechanism of enhanced non-photochemical energy dissipation

Abstract

The prasinophycean alga Mantoniella squamata uses in vivo an incomplete violaxanthin cycle. Although the violaxanthin cycle in Mantoniella is capable of converting violaxanthin to zeaxanthin, in intact cells only antheraxanthin accumulates during periods of strong illumination. Antheraxanthin enhances non-photochemical quenching of chlorophyll¯uores-cence. Inhibition of antheraxanthin synthesis by the deepoxidase inhibitor dithiothreitol abolishes increased thermal energy dissipation. Antheraxanthin-dependent non-photochemical quenching, like zeaxanthin-mediated non-photochemical quenching in higher plants, is uncoupler-sensitive. Mantoniella squamata cells cultivated at high light intensities contain higher amounts of violaxanthin than cells grown at low light. The increased violaxanthin-cycle pool size in high-light-grown Mantoniella cells is accompanied by higher de-epoxidation rates in the light and by a greater capacity to quench chlorophyll¯uorescence non-photochemically. Antheraxanthin-dependent ampli®cation of non-photochemical quenching is discussed in the light of recent models developed for zeaxanthin-and diatoxanthin-mediated enhanced heat dissipation.Key words: Antheraxanthin ± Light adaptation ± Mantoniella ± Non-photochemical quenching of chlorophyll¯uorescence ± Violaxanthin cycle ± Zeaxanthin Abbreviations and symbols: Chl chlorophyll; Fm H ¯uores-cence yield under conditions of membrane energization or recovering¯uorescence after actinic illumination; Fm maximum uorescence level with PSII reaction centers closed;Fo minimum¯uorescence with open PSII reaction centers; LHC light-harvesting complex; LHCII light-harvesting complex of PSII; NPQ non-photochemical quenching; PFD photon¯ux density Correspondence to: C.

An original adaptation of photosynthesis in the marine green alga Ostreococcus

“…Whereas nonphotochemical dissipation of absorbed energy (NPQ) (32) could readily occur in OTH95 in high light, independent of the growth conditions (Table 1), NPQ could be observed in RCC809 only upon exposure of the cells to 100 E⅐m Ϫ2 ⅐s Ϫ1 for several days. This NPQ was paralleled by the accumulation (Table 1) of antheraxanthin [i.e., the only product of violaxanthin deepoxidation in Prasinophytes (33)], as expected if the extra PTOX-dependent ⌬pH generated at this light may sustain a greater activity of violaxanthin deepoxidase (32) in RCC809.…”

Role of the Reversible Xanthophyll Cycle in the Photosystem II Damage and Repair Cycle in Dunaliella salina

“…2D). Considering the proposed role of Z in photoprotection (Demmig et al, 1987;Gilmore and Yamamoto, 1993;DemmigAdams et al, 1996;Goss et al, 1998;Havaux and Niyogi, 1999), these results indicate that a constitutive presence of Z does not confer enhanced resistance to photooxidative damage in the zea1 mutant. To more rigorously assess the role of Z in the protection against photooxidative damage of PSII in chloroplasts, further detailed analysis was undertaken at the thylakoid membrane and molecular levels.…”

“…When levels of absorbed irradiance become lower than those required for the saturation of photosynthesis, Z is converted back to V by the enzyme Z epoxidase (Hager, 1980). This xanthophyll cycle is a dynamically regulated and reversible interconversion of V to A to Z, occurring in the thylakoid membrane of photosynthesis (Demmig et al, 1987;Gilmore and Yamamoto, 1993;Demmig-Adams et al, 1996;Goss et al, 1998;Havaux and Niyogi, 1999). Another acclimation mechanism entails reversible changes in the Chl antenna size of the PSs.…”

Altered xanthophyll compositions adversely affect chlorophyll accumulation and nonphotochemical quenching in Arabidopsis mutants

“…Violaxanthin would not be expected to quench (29). However, antheraxanthin is a photophysical homologue of lutein in vitro (29) and can contribute to quenching (22)(23)(24)51). Consequently, it is surprising that, if lutein (wild type) and zeaxanthin (aba1, lut2aba1) are abundant, quenching is rapid but is not so if antheraxanthin is abundant (lut2).…”